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cell biology (osmosis (is the movement of water molecules across a…
cell biology
osmosis
is the movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration
- the water molecules actually pass both ways through the membrane during osmosis. this happens because water molecules move about randomly all the time
- but because there are more water molecules on one side than on the other there's a steady net flow of water into the region with fewer water molecules i.e. into the stronger sugar solution.
- this means the stronger sugar solution gets more dilute the water acts like its trying to even up the concentration either side of the membrane
- a partially permeable membrane is ust one with very small holes in it. so small in fact only tiny molecules (like water) can pass through them, and bigger molecules
- osmosis is a type id diffusion- passive movement of water particles from an area of higher water concentration to an area of lower water concentration
diffusion
- that's all it is - just the natural tendency for stuff to spread out
- diffusion happens in both solutions and gases- that's because the particles in these substances are free to move around randomly
- its just the gradual movement of particles from places where there are lots of them to places where there are fewer of them
- the simplest type is when different gases diffuse through each other.
is the spreading out of particles from an area of higher concentration to an are of low concentration to a low concentration
active transport
- this means that the concentration gradient is the wrong way.
- the same process used in plant root issued here- active transport
- but- sometimes there's a lower concentration of notorious in the gut than there is in the blood
- active transport allows nutrients to be taken into the blood despite the fact that the concentration gradient is the wrong way.
- when there's a higher concentration of glucose and amino acids in the gut the diffuse naturally into the blood.
exchanging substances
in humans urea (a waste product produced from the breakdown of proteins) diffuses from cells into the blood plasma for removal from the body by the kidneys.
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